Reactions of Acids

📚 Key Concepts

🔹 Real-Life Example

When you put an iron nail in lemon juice (citric acid), you’ll notice bubbles forming. This is hydrogen gas being released! The nail slowly dissolves as the acid reacts with the metal. This is why we don’t store pickles in metal containers – the acids would corrode the metal and spoil the food.

🧪 Important Reactions

🔸 Acid + Metal → Salt + Hydrogen Gas

Examples:

• Zn + 2HCl → ZnCl₂ + H₂↑
• Fe + H₂SO₄ → FeSO₄ + H₂↑
• 2Al + 6HCl → 2AlCl₃ + 3H₂↑

Test for Hydrogen Gas: Bring a burning splinter near the gas – it burns with a “pop” sound.

🔸 Acid + Metal Carbonate → Salt + CO₂ + Water

Examples:

• CaCO₃ + 2HCl → CaCl₂ + CO₂↑ + H₂O
• Na₂CO₃ + H₂SO₄ → Na₂SO₄ + CO₂↑ + H₂O

Test for CO₂: Pass the gas through lime water – it turns milky.

🔸 Acid + Metal Bicarbonate → Salt + CO₂ + Water

Example:

• NaHCO₃ + HCl → NaCl + CO₂↑ + H₂O

🔸 Acid + Base → Salt + Water (Neutralization)

Examples:

• HCl + NaOH → NaCl + H₂O
• H₂SO₄ + 2KOH → K₂SO₄ + 2H₂O

🔸 Acid + Metal Oxide → Salt + Water

Examples:

• 2HCl + CuO → CuCl₂ + H₂O
• H₂SO₄ + ZnO → ZnSO₄ + H₂O

🔍 Advanced: Why These Reactions Occur

Metal oxides and metal carbonates are basic in nature, so they neutralize acids. This is why antacids (which contain metal carbonates) relieve acidity in the stomach